1. Field of the Invention
The present invention relates to the production of plural component fibers with dissolvable polymer components.
2. Description of the Related Art
Plural component fibers with dissolvable components are useful for a variety of applications. For example, islands-in-the-sea (I/S) fibers having a dissolvable sea section are often formed as intermediate products for forming ultra-fine fibers (e.g., fibers having cross-sectional dimensions in the micrometer or nanometer range) for certain textile applications. Techniques for forming ultra-fine fibers utilizing extruded I/S fibers as precursors to forming the ultra-fine fibers are typically more effective than other known techniques, such as meltblowing, electrospinning and fiber splitting. In a typical I/S technique, ultra-fine fibers are produced by combining the high production rates of normal melt spinning to form the I/S fibers, followed by separation of the island sections to form the ultra-fine fibers by dissolving the sea section of the I/S fibers.
While the I/S process is highly effective and desirable in producing ultra-fine fibers, there are certain problems associated with this process. In particular, the costs associated with the sacrificial polymer (i.e., the sea section) required to form a conventional I/S fiber having a round cross-sectional geometry can adversely impact the economies associated with producing the resultant ultra-fine fibers. In addition, it becomes increasingly difficult to separate island sections from the sea section to form the ultra-fine fibers as the number of island sections within an I/S fiber increases. Further, the time required for separating island sections by dissolving away the sea section in a conventional I/S fiber could be detrimental to the resultant ultra-fine fibers. For example, bicomponent combinations of polyester (PET)/easy soluble polyester (ESPET) are utilized in many textile I/S fiber applications, where ESPET forms the sea section and PET forms the island sections. After formation of the I/S fibers, the ESPET sea section is dissolved away from the PET island sections in a suitable solvent (e.g., sodium hydroxide). However, if the ESPET sea section dissolves too slowly, the solvent can also dissolve some of the PET island sections before they are sufficiently removed from the ESPET sea section. In such a scenario, it would be desirable to effectively control the rate of dissolution of the ESPET sea section to ensure separation of the PET island sections with minimal or no dissolution to PET island sections.
Plural component fibers having two or more fiber sections including dissolvable components that dissolve at varying rates would also be desirable for use in fields other than textile applications. For example, a plural component fiber that includes two or more sections that can be dissolved at selected rates would be useful for certain medical applications that require a controlled exposure or release of a particular component disposed within the fiber.
Thus, it is desirable to provide a plural component fiber that includes one or more dissolvable components, where the dissolution rate of the dissolvable components is selectively controlled.